This application claims the priority of German Application No. 10 2006 004 258.1, filed Jan. 31, 2006, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to brake regulating systems and methods for motor vehicles having an electronic control unit, by which an automatic parking brake function is activatable at a standstill of the motor vehicle, deactivation of which is performed as a function of the instantaneous drive torque.
Methods and systems which are to be used for preventing vehicles from rolling away—particularly, but not necessarily, on slopes—are known from various patent applications and patent specifications, for example, from DE 199 50 034 A1 (having U.S. counterpart U.S. Pat. No. 6,439,675 B1), DE 196 11 359 C1 (having U.S. counterpart U.S. Pat. No. 5,979,619); DE 199 50 162 B4; DE 198 48 448 C2 (having U.S. counterpart U.S. Pat. No. 6,315,372 B1); DE 101 51 846 B4; DE 199 41 482 A1 (having U.S. counterpart U.S. Pat. No. 6,814,414 B1), and more. Usually, in at least one operating state upon actuating a brake pedal or due to another actuating element, braking force is maintained or actively built up on at least one wheel of the vehicle dependently or independently of the dimension of the pedal actuation or another actuating element. Various entry and/or trigger conditions are provided jointly, or alternatively, for the activation and deactivation of the function.
These methods and devices are known, for example, under the names starting assistant, hill assistant, hill holder, or automatic hold. In summary, these methods are referred to in the following as automatic parking brake functions. All of these automatic parking brake functions share the feature, for example, of a hydraulic, mechanical, electrohydraulic, electromechanical, pneumatic, or electronically controllable brake system. By using the controllable braking system, the vehicle is stopped and is prevented from rolling. Methods are also known in which rolling of the vehicle is prevented via the transmission (in particular, such as automatic transmissions). In all of these functions, for example, the function is activated by actuating the brake pedal or the hand brake, or via switching elements connected thereto, and/or also other actuating elements (such as switches, buttons, etc.). Deactivation is performed via the same or also other measures (such as gas pedal setting, clutch signal, drive torque signals of the engine, etc., and also after passage of a defined retention time).
Important further required measures, control signals, or switching devices for implementing the functions are, for example, usually one or more velocity signals for detecting the vehicle standstill, mechanical, pneumatic, or hydraulic actuators (electrohydraulic, electropneumatic, or electrical actuators are also contemplated, in principle) in the wheel brakes and/or in the supply lines to the wheel brakes, via which the brake action may be built up and reduced, and/or at least temporarily maintained (e.g., control/regulating valves integrated in the form of an existing control or regulating unit, such as ABS, ASC/ASR, DSC/ESP/EHB systems), possibly also longitudinal acceleration or inclination sensors. By using these measures, the roadway longitudinal inclination may be ascertained and the braking force necessary for a secure standstill of the vehicle and the starting torque required for the roadway inclination may be determined and one or more pressure sensors, with the aid of which the brake pressure and/or the applied braking torque on the wheel brakes(s), may be ascertained.
An aspect of the present invention is to disengage the braking torque as necessary, and precisely, in a targeted manner at a sufficiently high starting torque so that the vehicle does not roll in an undesired way prematurely against the desired travel direction, thus possibly causing accident situations. Additionally, the vehicle does not have to start up against the brake retaining force and thus reductions in comfort, which may otherwise arise due to too long a braking force retention (caused by a requested starting torque, which is too high) can be minimized.
The present invention thus provides a brake regulating system for motor vehicles having an electronic control unit, by which an automatic parking brake function is activatable at a standstill of the motor vehicle, deactivation of which is performed as a function of the instantaneous drive torque. In the event of an activated parking brake function, a deactivation of the parking brake function may be suppressed if, on the basis of a function executed at a standstill of the motor vehicle, an automatic increase of the drive torque, which does not result from a starting command of the driver, is necessary. Advantageous refinements of the present invention are described and claimed herein.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.